You will be over exposing by 1/3rd stop. Slightly over exposing color neg film will add density, which will make the colors pop a little more and even tighten grain a little. Although you want to actually go at least 2/3rds over to achieve that. Point being rating it at 400ASA will do more good than bad. You want to avoid under exposing instead when it comes to color negative. I've never owned that camera, but pretty sure you can set your own f stops manually.. should you want to rate it at box speed or over expose
This is the 1970 Leicina Super, not the Special I haven't got enough budget for a Special this year. Though I will surely try and get one, if I turn out to be even just half decent with the Super.
So all I have (according to the manual) is that red button with a sort of T
According to the manual, it boils down to telling the camera whether the film is colour of B&W (red vs BW side) and whether it's a T or a D. It doesn't explicitly say it will read the notches, but so I would expect, given that I have no way to state a number anywhere.
The second knob allows to over/under expose by 1 stop (half stop levels available). But half a stop from what? It must be what it reads from the notches, I should think.
Over-exposing is indeed totally fine, I just wish to have an idea of what the camera will use as a base exposition.